1. Field of the Invention
This invention relates to improvements in centrifugal filters and particularly to a unique centrifugal oil filter-adaptor assembly in which only the rotor is disposable.
2. Prior Art
Centrifugal filters for separating contaminants from contaminated liquids and particularly for separating solid matter from oil are known in the art, especially for use in internal combustion engines. Numerous examples of such exist in the prior art of centrifugal oil filters.
Centrifugal oil filters greatly improve engine durability, especially the durability of piston rings, due to the removal of contaminants from the oil. For example, while conventional media filters can remove contaminants down to the particle size range of about 10 microns, centrifugal filters can remove contaminants down to a particle size of 1/2 micron. However centrifugal filters have not found favor in the U.S. due in large part to their original cost and the maintenance cost of cleaning the rotor.
It is therefore highly desirable to have a centrifugal oil filter which is inexpensive and which is disposable. That is, a desirable filter would be constructed of such material that it would be inexpensive enough to be completely disposable after it had become clogged with dirt filtered from the oil, while at the same time it would be maintenance-free and efficient while in use.
The advantages of centrifugal oil filters over conventional filters and the desirability of a disposable centrifugal filter are taught in numerous prior art patents, for example, U.S. Pat. Nos. 4,106,689, 4,288,030 and 4,400,167. In all of these patents there is an attempt to make the construction inexpensive so that the entire filter rotor, casing and all, may be discarded after use. Such constructions have not met with a significant degree of commercial success for one reason or another. Possibly one reason is the difficulty in making an entirely disposable filter sturdy enough to adequately support an efficient and maintenance-free rotor and/or inexpensive enough so as to make it economical.
It is also known in the art to provide centrifugal oil filters in which only a rotor unit is disposable. That is, the filter assembly was of such construction that it could be opened and the rotor unit discarded after it became dirty from accumulation of material filtered from the oil. Such is taught, for example, in British Patent Specification No. 1,035,542.
Even in view of the teachings of the prior art as set forth above, there remains a problem of having a simple, effective, maintenance-free and inexpensive centrifugal oil filter construction in which the rotor only may be discarded while providing a rigid permanent support shaft for the rotor as well as a means for removing and installing the filter with conventional tools.
Additionally, in the art of centrifugal filters it is known to be desirable to vent the inside of a casing in which a centrifugal rotor operates however, such prior art venting was done to atmosphere, creating pollution control problems.